Patients with ocular toxoplasmosis, pars planitis, sarcoidosis, Behcet's disease, chorioretinitis of unknown origin, and iridocyclitis of unknown etiology are being studied to determine the phenotype frequency of the HLA, ABO, and B-cell alloantigens. Since the B-cell alloantigens or DR antigens are thought to play a role in the immunologic response to antigens, these findings will complement other immune uveitis studies being simultaneously carried out.